When a conventional conference call is set up within a communications network a Virtual Call Admissions Control (VCAC) on a server controlling the call will allocate bandwidth to the conference call according to rules set up on the server. The VCAC is responsible for monitoring the use of bandwidth within the network and permitting or denying calls according to the amount of available bandwidth.
Typically, when a conference call is set up on the network the VCAC will apply the assumption that each participant in the conference call requires a duplex link, i.e. a link which allows a user simultaneously both to listen to the conference and to be heard, when calculating the amount of bandwidth to allocate the conference call. However, as only one person is likely to be speaking at any one time the majority of this bandwidth allocation will remain unused due to silence suppression on the remaining lines.
This results in other calls which are requested to be set up after such a conference call has been set up, being refused by the VCAC even though it is highly likely that there is available bandwidth for transmitting one or more additional call. Furthermore, such bandwidth overprovisioning places a limit on the number of participants which can take part in the conference call.
Another way to try to solve the above problem is to estimate the bandwidth usage of the conference call at some value less than that required for a full set of duplix links. In this way a more realistic provisioning of the link for new calls which are subsequently made can be achieved. However, once the estimate has been made there is typically no way to enforce bandwidth restrictions on the conference call.
Therefore, the VCAC may set up new calls using the conference call's assumed bandwidth to estimate the amount of available bandwidth. If the conference call exceeds this bandwidth it is likely that the Quality of Service of the call is reduced resulting in impaired reception of any calls being transmitted down the link on which bandwidth has been exceeded.